Blue Hawaii BJT Build thread

[starcat]

Thread seems to be dead, all builders left 🙂

[mwl168]

The original design of Blue Hawaii uses 2SK170 BL grade which has the IDSS grade in the same range of LSK389B.

Double check the data sheet to confirm.

2SK170/LSK389 are JFET so using either 10K or 50K volume pot should be fine. 10K pot may be more ideal if your source can drive it.

[mwl168]

Switched from Megatron to the Blue Hawaii this morning. Different sound signature but equally as satisfying. 

This one is not the BJT version but the one that uses 2SK216/2SJ79 with cascoded CCS and adjustable plate current. 

 

[audiostar]

Very interesting, someone here is calling the BH an "Orpheus clone"... @kevin gilmore

[kevin gilmore]

that person is a moron. the orpheus has 3 capacitor coupled stages. the BH is completely dc coupled.

[chinsettawong]

Maybe he was referring to the DIY headphones he was testing.

[spritzer]

Yeah, those are the one Milos was working on. 

[simmconn]

TL; DR: I’ve wanted to build a Blue Hawaii ever since I read about it on head-wize. I finally got around building a mini BH-BJT packed into a small enclosure like a can of sardines. Many small tweaks were done in attempt to reach the measured performance of the original Blue Hawaii. The details of the journey are recorded here.

Many thanks to Dr. Kevin Gilmore for designing this legendary project. Thanks to Kerry, JimL, Joamat and many others for making it such a fun journey.

KGBH1.pdf

[JoaMat]

Jolly good work!

Thank you for the excellent PDF document. Lots of interesting stuff there.

[Kerry]

^This.  

[MLA]

On 1/26/2023 at 9:20 AM, simmconn said:

Many small tweaks were done in attempt to reach the measured performance of the original Blue Hawaii.

Working on a BH at the moment, and given what you found regarding Cob for 2690; do you think it would be worthwhile to use TTC004b instead, or is the difference too small? I guess you may have checked it but discarded it as an option?  

[Helium]

On 5/3/2024 at 9:57 AM, MLA said:

Working on a BH at the moment, and given what you found regarding Cob for 2690; do you think it would be worthwhile to use TTC004b instead, or is the difference too small? I guess you may have checked it but discarded it as an option?  

Seems that KSA1220AYS may also be replaced with TTA004B,Q? The latter also seems better.

[hyperma]

The 2SC5460B is back, renamed as TTC5460B, a TO-126 packaged 2SC6127 given us more possibilities on construction, maybe it's time to start a new project?

[Helium]

Did anyone experience that BH BJT is quieter than other Stax amps? Like 15 o'clock vs 12-13 o'clock on T2. Is there any way to increase gain?

[jamesmking]

20 hours ago, Helium said:

Did anyone experience that BH BJT is quieter than other Stax amps? Like 15 o'clock vs 12-13 o'clock on T2. Is there any way to increase gain?

As far as I know most of Kevin's valve and value/transistor hybrids aim for a gain of 1000x - thats what the mostly modern T2 has and I think the blue BJT blue Hawaii. The only exception I have experienced is the (standard) EL34 Megatron which has lower gain.

Edited Wednesday at 11:45 AM by jamesmking

[Helium]

On 4/16/2025 at 2:42 PM, jamesmking said:

As far as I know most of Kevin's valve and value/transistor hybrids aim for a gain of 1000x - thats what the mostly modern T2 has and I think the blue BJT blue Hawaii. The only exception I have experienced is the (standard) EL34 Megatron which has lower gain.

It's definitely quieter. Reasonable loudness is reached at 15-16 o'clock.

Pot is 10k series type, B+/B- is 400vdc, but those don't affect volume.

The only change I made is I used TTA004B,Q and TTC004B,Q instead of KSC2690AYS and KSA1220AYS. I doubt that it could be the reason as they are direct replacements.

It would be nice to find a solution.

Edited 1 hour ago by Helium

[Helium]

Edit: one idea, is maybe log taper of the pot was too steep. Need to try another one.

Edited 52 minutes ago by Helium